The Cisneros U.S. Pat. No. 4,664,712 discloses thermal insulating materials formed by the curing and drying of a composition comprising an expanded siliceous inorganic aggregate, aqueous sodium silicate, kaolin, mica, inorganic reinforcing fiber and a filler. Other thermal insulating materials and compositions are also known in the art. It is often desirable that such materials exhibit fire-retardant properties, whereby a fire-retardant additive is required.